Preheat oven to 400° F. Bring a large pot of water to a boil. Place the zucchini in a large baking dish in a single layer and drizzle with the oil, chili flakes, and 3 tablespoons of the Parmesan, then season with the pepper and ½ teaspoon of the salt. Add the garlic and roast for 20 minutes, tos...